Climate change to drive annual temps to new highs within a generation, study says

By Michael Pearson, CNN

Updated 2:45 PM ET, Thu October 10, 2013

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An enormous iceberg breaks off the Knox Coast in the Australian Antarctic Territory.

Story highlights

A new study sets dates when average temperatures will exceed current records

Some cities in the tropics will hit the milestone by 2020, the study says

By 2100, average temps will be higher than any time since at least 1860, study says

Limiting emissions will slow down but not stop the changes, authors say

Average annual temperatures will start to consistently exceed the highest levels previously recorded in as little as seven years in tropical hotspots and within four decades for the majority of the globe if nothing is done to stop climate change, according to a new study published Thursday in the journal Nature.

And by the end of the century, monthly average temperatures will be higher than at any time since at least 1860, according to the study, led by University of Hawaii geographer Camilo Mora.

The effects will be felt first in tropical climates, with the annual temperature range rising beyond the historical range in Manokwari, Indonesia, in 2020, according to a map that accompanies the study on the University of Hawaii website.

Mexico City's date is 2031. It's 2046 in Orlando, and a year later in Washington and New York, according to the group. Anchorage, Alaska, doesn't climb on board until 2071.

"The results shocked us. Regardless of the scenario, changes will be coming soon," Mora said in a statement posted by the university. "Within my generation, whatever climate we were used to will be a thing of the past."

According to the research, which assesses the impact of warming using an average of well-accepted computer climate models, the average annual global temperature will move "to a state continuously outside the bounds of historical variability" in 2047 if no efforts are made to slow global warming.

Such changes can be put off some 20 years if greenhouse gas emissions are stabilized, the study says.

What exactly does this mean? If you live in the Midwest, think back to the extreme heat and drought of the past few years, CNN meteorologist Brandon Miller said.

Russian residents can remember the heat in 2010, Europeans, 2003.

"Well, that's going to be a normal year, not even an extreme," Miller said. "Those kinds of extreme become an average.

"It doesn't mean that every day is going to be a record high," he said. "There's still variability from month to month, day to day. But that overall year is going to be hotter than any of the years we've experienced."

The study comes two weeks after the release of a United Nations report expressing widespread, rising confidence among scientists the climate is already warming and that humans are responsible for at least half of the increase in global surface temperatures since the 1950s.

"This work demonstrates that we are pushing the ecosystems of the world out of the environment in which they evolved into wholly new conditions that they may not be able to cope with. Extinctions are likely to result," the University of Hawaii quoted Ken Caldeira of the Carnegie Institution for Science's Department of Global Ecology as saying. "Some ecosystems may be able to adapt, but for others, such as coral reefs, complete loss of not only individual species but their entire integrity is likely."

Caldeira was not involved in the study, according to the school.

While many places around the world won't see their climate tip outside of historical ranges for many decades, that doesn't mean climate change won't be affecting those places before then, the authors contend.

And more immediate, and rapid, changes in the tropics will spell trouble worldwide, they contend.

Much of the world's population lives in tropical climates in countries without sufficient resources to adapt to the changing climate, the authors say. More than 5 billion people live in areas that would be affected by climate change by 2050 should nothing be done to slow its pace, the authors say. A significant portion of the world's food supply and much of global biodiversity also comes from tropical regions, they say.

"Our results suggest that countries first impacted by unprecedented climates are the ones with the least capacity to respond," co-author Ryan Longman said in the university statement. "Ironically, these are the countries that are least responsible for climate change in the first place."

"This suggests that any progress to decrease the rate of ongoing climate change will require a bigger commitment from developed countries to decrease their emissions, but will also require more extensive funding of social and conservation programmes in developing countries," the authors write in their study.